Laryngoscopes are routinely used to facilitate endotracheal intubation of patients, to provide an air passage for administration of anesthesia and/or to establish an airway that is obstructed. In addition, laryngoscopes are commonly used in surgery to displace pharyngeal tissues to permit direct inspection of the larynx (i.e. direct laryngoscopy).
Anesthesiologists use laryngoscopes that are L-shaped having a handle connected to single curved or straight blade. Otolaryngologists typically use a tubed laryngoscope to view the larynx and operate endoscopically on the true vocal cords (i.e. glottis).
Modern adjustable laryngoscopes, the forerunners of which first appeared in the early decades of the twentieth century, are all bivalved glottiscopes designed for use on the true vocal cords. They characteristically possess long and narrow blades. Adjustable glottiscopes are designed to be inserted into the mouth and down the throat. The superior blade engages the tongue and supraglottis while the inferior blade engages the roof of the mouth and the posterior pharyngeal wall. The length of the blades allows for exposure of the true vocal cords. Examples of such laryngoscopes include the Weerda Laryngoscope (Karl Storz Co., Culver City, Calif.) and the Steiner Laryngoscope (Richard Wolf Co., Rosemont, Ill.). They are conveniently used for surgery in the lower larynx (true vocal cords/glottis).
Nevertheless use of these instruments may be ineffective for surgery in the supraglottis (epiglottis and false vocal cords) and lower pharynx (base of tongue, pharyngoepiglottic folds, and posterior pharyngeal wall). This is due primarily to the length and the narrowness of the adjustable blades of conventional adjustable glottiscopes. In addition, when exposing the larynx, these conventional instruments are designed to extend both the head and neck by tilting the head backwards and distending the lower jaw. Adequate exposure of the supraglottis for endoscopic surgery, especially with the carbon dioxide laser, requires true suspension which involves flexion of the neck, while extending the head (the "sniffing" position).
Most significantly, the distal lumen of conventional adjustable glottiscopes, formed by the ends of the long and narrow blades, has a surface area that is small in relationship to the surface area of the supraglottis. Endoscopic laser surgery of the supraglottis is precluded by conventional adjustable glottiscopes because there is insufficient exposure of the supraglottic surgical field.